Lowering Onset Temperature and Improving Oxidation of Aluminum Alloys Containing Gallium and Indium

ABSTRACT The formation of an inhibiting oxide layer on the surface of aluminum not only offers significant thermal stability at ambient temperatures but also presents a significant barrier toward intentional ignition in energetic formulations. Therefore, we demonstrate that the oxide‐disrupting properties of gallium and indium in aluminum–gallium/indium alloys significantly reduce the onset temperature for oxidation and enhance the overall reactivity of the aluminum while maintaining reasonable thermal stability. This increased oxidation is likely due to weakened oxide layer adherence through significantly reduced surface energies. Neat, spherical micron‐aluminum powders oxidize between 7 and 14 wt.% of their total mass by 1200°C in a thermogravimetric analyzer operated in 20% oxygen‐containing argon. In contrast, similarly sized aluminum–gallium/indium alloy powders fabricated using mechanical processing (containing 3–16 wt.% Ga–In) oxidize 49%–86% of their total mass under the same conditions. While the increased reactivity of the mechanically processed aluminum–gallium/indium alloys can be partially explained by an increase in surface area due to mechanical processing, neat aluminum particles with similar surface areas are not as reactive, oxidizing only 22.4 wt.% of the active aluminum by 1200°C.